Intermittent out of service recovery on accessory device

ABSTRACT

This disclosure relates to out of service recovery techniques for an accessory device. According to some embodiments, the accessory device may receive cellular communication system selection information from a paired device. The accessory device may store the communication system selection information. At some point, it may be determined that the accessory device has lost cellular communication service. The accessory device may perform a cellular communication service scan utilizing the system selection information received from the paired device along with its own historical information and location based frequency lists.

TECHNICAL FIELD

The present application relates to wireless communication, including totechniques for an accessory device to recover from intermittent out ofservice conditions.

DESCRIPTION OF THE RELATED ART

Wireless communication systems are rapidly growing in usage. Further,wireless communication technology has evolved from voice-onlycommunications to also include the transmission of data, such asInternet and multimedia content.

Mobile electronic devices may take the form of smart phones or tabletsthat a user typically carries. Wearable devices (also referred to asaccessory devices) are a newer form of mobile electronic device, oneexample being smart watches. Typically, wearable devices have relativelylimited wireless communications capabilities and typically have smallerbatteries than larger portable devices, such as smart phones andtablets. In general, it would be desirable to reduce the powerrequirements of communication devices. Therefore, improvements in thefield are desired.

SUMMARY

Embodiments are presented herein of, inter alia, systems, apparatuses,and methods for an accessory device to recover from intermittent out ofservice conditions.

According to the techniques described herein, an accessory device maypair with another device (that may be referred to as a “second device”or “paired device”). This may include establishing a pairingrelationship using a short range communication technology such asBluetooth, Wi-Fi peer-to-peer, near field communication (NFC), etc.

The paired device may provide (e.g., via the short range communicationtechnology) cellular communication system selection information to theaccessory device. The cellular communication system selectioninformation may include information found and/or used during cellularcommunication system selection by the paired device, such as any or allof a current cell ID of a cell on which the paired device is camped, aradio access technology with which the paired device is camping on thecell, a list of frequencies on which the paired device has been able todetect cellular communication system information, a list of frequencieson which neighboring cells to the current cell on which the paireddevice is camped are deployed, a public land mobile network on which thepaired device is currently (or most recently was) registered, a list ofcandidate cellular communication system frequencies associated with acurrent location of the paired device, and/or any of various other typesof information.

The accessory device may utilize the cellular communication systemselection information from the paired device as part of a cellularcommunication service scan if and when the accessory device losescellular communication service, potentially including times when thepairing with the paired device is also lost (e.g., if the accessorydevice is taken on a run or hike without the paired device, amongvarious possible reasons).

In some instances, the accessory device may filter some or all of thecellular communication system selection information based oncharacteristics of the accessory device that differ from the paireddevice prior to utilizing the information as part of its cellularcommunication service scan. For example, if the accessory device has aless sensitive antenna arrangement than the paired device, a (e.g.,relatively high) signal strength threshold associated with the accessorydevice may be used to filter out frequencies on which cellularcommunication system information was detected by the paired device withsignal strength below the signal strength threshold associated with theaccessory device from being scanned as part of the cellularcommunication service scan (e.g., at least initially), as onepossibility.

In some instances, the location and/or motion state of the accessorydevice may also or alternatively be considered as part of a cellularcommunication service scan when out-of-service. For example, theaccessory device may determine its location, determine a set ofcandidate cellular communication system frequencies associated with itscurrent location, and perform the cellular communication service scanbased at least in part on that set of candidate cellular communicationsystem frequencies. One or more filters based on characteristics of theaccessory device, subscription characteristics, etc., may also beapplied to the location based set of frequencies. According to someembodiments, a length of time for which the location based set offrequencies is considered valid may be determined based at least in parton the motion state of the accessory device. For example, locationinformation for a rapidly moving accessory device may become stale morequickly than a slowly moving or stationary accessory device.

The techniques described herein may be implemented in and/or used with anumber of different types of devices, including but not limited tocellular phones, tablet computers, accessory and/or wearable computingdevices, portable media players, cellular base stations and othercellular network infrastructure equipment, servers, and any of variousother computing devices.

This summary is intended to provide a brief overview of some of thesubject matter described in this document. Accordingly, it will beappreciated that the above-described features are merely examples andshould not be construed to narrow the scope or spirit of the subjectmatter described herein in any way. Other features, aspects, andadvantages of the subject matter described herein will become apparentfrom the following Detailed Description, Figures, and Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present subject matter can be obtainedwhen the following detailed description of the embodiments is consideredin conjunction with the following drawings.

FIG. 1 illustrates an example wireless communication system including anaccessory device, according to some embodiments;

FIG. 2 illustrates an example system where an accessory device canselectively either directly communicate with a cellular base station orutilize the cellular capabilities of an intermediate or proxy devicesuch as a smart phone, according to some embodiments;

FIG. 3 is a block diagram illustrating an example wireless device,according to some embodiments;

FIG. 4 is a block diagram illustrating an example base station,according to some embodiments; and

FIG. 5 is a flowchart diagram illustrating an exemplary method for outof service recovery by an accessory device, according to someembodiments.

While the features described herein are susceptible to variousmodifications and alternative forms, specific embodiments thereof areshown by way of example in the drawings and are herein described indetail. It should be understood, however, that the drawings and detaileddescription thereto are not intended to be limiting to the particularform disclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the subject matter as defined by the appended claims.

The term “configured to” is used herein to connote structure byindicating that the units/circuits/components include structure (e.g.,circuitry) that performs the task or tasks during operation. As such,the unit/circuit/component can be said to be configured to perform thetask even when the specified unit/circuit/component is not currentlyoperational (e.g., is not on). The units/circuits/components used withthe “configured to” language include hardware—for example, circuits,memory storing program instructions executable to implement theoperation, etc. Reciting that a unit/circuit/component is “configuredto” perform one or more tasks is expressly intended not to invokeinterpretation under 35 U.S.C. §112(f) for that unit/circuit/component.

DETAILED DESCRIPTION Terminology

The following are definitions of terms used in this disclosure:

Memory Medium—Any of various types of non-transitory memory devices orstorage devices. The term “memory medium” is intended to include aninstallation medium, e.g., a CD-ROM, floppy disks, or tape device; acomputer system memory or random access memory such as DRAM, DDR RAM,SRAM, EDO RAM, Rambus RAM, etc.; a non-volatile memory such as a Flash,magnetic media, e.g., a hard drive, or optical storage; registers, orother similar types of memory elements, etc. The memory medium mayinclude other types of non-transitory memory as well or combinationsthereof. In addition, the memory medium may be located in a firstcomputer system in which the programs are executed, or may be located ina second different computer system which connects to the first computersystem over a network, such as the Internet. In the latter instance, thesecond computer system may provide program instructions to the firstcomputer for execution. The term “memory medium” may include two or morememory mediums which may reside in different locations, e.g., indifferent computer systems that are connected over a network. The memorymedium may store program instructions (e.g., embodied as computerprograms) that may be executed by one or more processors.

Carrier Medium—a memory medium as described above, as well as a physicaltransmission medium, such as a bus, network, and/or other physicaltransmission medium that conveys signals such as electrical,electromagnetic, or digital signals.

Programmable Hardware Element—includes various hardware devicescomprising multiple programmable function blocks connected via aprogrammable interconnect. Examples include FPGAs (Field ProgrammableGate Arrays), PLDs (Programmable Logic Devices), FPOAs (FieldProgrammable Object Arrays), and CPLDs (Complex PLDs). The programmablefunction blocks may range from fine grained (combinatorial logic or lookup tables) to coarse grained (arithmetic logic units or processorcores). A programmable hardware element may also be referred to as“reconfigurable logic”.

Computer System—any of various types of computing or processing systems,including a personal computer system (PC), mainframe computer system,workstation, network appliance, Internet appliance, personal digitalassistant (PDA), television system, grid computing system, or otherdevice or combinations of devices. In general, the term “computersystem” can be broadly defined to encompass any device (or combinationof devices) having at least one processor that executes instructionsfrom a memory medium.

User Equipment (UE) (or “UE Device”)—any of various types of computersystems devices which are mobile or portable and which performs wirelesscommunications. Examples of UE devices include mobile telephones orsmart phones (e.g., iPhone™, Android™-based phones), portable gamingdevices (e.g., Nintendo DS™, PlayStation Portable™, Gameboy Advance™,iPhone™), laptops, wearable devices (e.g. smart watch, smart glasses),PDAs, portable Internet devices, music players, data storage devices, orother handheld devices, etc. In general, the term “UE” or “UE device”can be broadly defined to encompass any electronic, computing, and/ortelecommunications device (or combination of devices) which is easilytransported by a user and capable of wireless communication.

Wireless Device—any of various types of computer system devices whichperforms wireless communications. A wireless device can be portable (ormobile) or may be stationary or fixed at a certain location. A UE is anexample of a wireless device.

Communication Device—any of various types of computer systems or devicesthat perform communications, where the communications can be wired orwireless. A communication device can be portable (or mobile) or may bestationary or fixed at a certain location. A wireless device is anexample of a communication device. A UE is another example of acommunication device.

Base Station—The term “Base Station” (also called “eNB”) has the fullbreadth of its ordinary meaning, and at least includes a wirelesscommunication station installed at a fixed location and used tocommunicate as part of a wireless cellular communication system.

Link Budget Limited—includes the full breadth of its ordinary meaning,and at least includes a characteristic of a wireless device (a UE) whichexhibits limited communication capabilities, or limited power, relativeto a device that is not link budget limited, or relative to devices forwhich a radio access technology (RAT) standard has been developed. A UEthat is link budget limited may experience relatively limited receptionand/or transmission capabilities, which may be due to one or morefactors such as device design, device size, battery size, antenna sizeor design, transmit power, receive power, current transmission mediumconditions, and/or other factors. Such devices may be referred to hereinas “link budget limited” (or “link budget constrained”) devices. Adevice may be inherently link budget limited due to its size, batterypower, and/or transmit/receive power. For example, a smart watch that iscommunicating over LTE or LTE-A with a base station may be inherentlylink budget limited due to its reduced transmit/receive power and/orreduced antenna. Wearable devices, such as smart watches, are generallylink budget limited devices. Alternatively, a device may not beinherently link budget limited, e.g., may have sufficient size, batterypower, and/or transmit/receive power for normal communications over LTEor LTE-A, but may be temporarily link budget limited due to currentcommunication conditions, e.g., a smart phone being at the edge of acell, etc. It is noted that the term “link budget limited” includes orencompasses power limitations, and thus a power limited device may beconsidered a link budget limited device.

Processing Element (or Processor)—refers to various elements orcombinations of elements. Processing elements include, for example,circuits such as an ASIC (Application Specific Integrated Circuit),portions or circuits of individual processor cores, entire processorcores, individual processors, programmable hardware devices such as afield programmable gate array (FPGA), and/or larger portions of systemsthat include multiple processors.

Automatically—refers to an action or operation performed by a computersystem (e.g., software executed by the computer system) or device (e.g.,circuitry, programmable hardware elements, ASICs, etc.), without userinput directly specifying or performing the action or operation. Thusthe term “automatically” is in contrast to an operation being manuallyperformed or specified by the user, where the user provides input todirectly perform the operation. An automatic procedure may be initiatedby input provided by the user, but the subsequent actions that areperformed “automatically” are not specified by the user, i.e., are notperformed “manually”, where the user specifies each action to perform.For example, a user filling out an electronic form by selecting eachfield and providing input specifying information (e.g., by typinginformation, selecting check boxes, radio selections, etc.) is fillingout the form manually, even though the computer system must update theform in response to the user actions. The form may be automaticallyfilled out by the computer system where the computer system (e.g.,software executing on the computer system) analyzes the fields of theform and fills in the form without any user input specifying the answersto the fields. As indicated above, the user may invoke the automaticfilling of the form, but is not involved in the actual filling of theform (e.g., the user is not manually specifying answers to fields butrather they are being automatically completed). The presentspecification provides various examples of operations beingautomatically performed in response to actions the user has taken.

FIG. 1—Wireless Communication System

FIG. 1 illustrates an example of a wireless cellular communicationsystem. It is noted that FIG. 1 represents one possibility among many,and that features of the present disclosure may be implemented in any ofvarious systems, as desired. For example, embodiments described hereinmay be implemented in any type of wireless device, or any type ofcommunication device. The wireless embodiment described below is oneexample embodiment.

As shown, the exemplary wireless communication system includes acellular base station 102, which communicates over a transmission mediumwith one or more wireless devices 106A, 106B, etc., as well as accessorydevice 107. Wireless devices 106A, 106B, and 107 may be user devices,which may be referred to herein as “user equipment” (UE) or UE devices.

The base station 102 may be a base transceiver station (BTS) or cellsite, and may include hardware that enables wireless communication withthe UE devices 106A, 106B, and 107. The base station 102 may also beequipped to communicate with a network 100 (e.g., a core network of acellular service provider, a telecommunication network such as a publicswitched telephone network (PSTN), and/or the Internet, among variouspossibilities). Thus, the base station 102 may facilitate communicationamong the UE devices 106 and 107 and/or between the UE devices 106/107and the network 100. In other implementations, base station 102 can beconfigured to provide communications over one or more other wirelesstechnologies, such as an access point supporting one or more WLANprotocols, such as 802.11 a, b, g, n, ac, ad, and/or ax, or LTE in anunlicensed band (LAA).

The communication area (or coverage area) of the base station 102 may bereferred to as a “cell.” The base station 102 and the UEs 106/107 may beconfigured to communicate over the transmission medium using any ofvarious radio access technologies (RATs) or wireless communicationtechnologies, such as GSM, UMTS (WCDMA, TDS-CDMA), LTE, LTE-Advanced(LTE-A), HSPA, 3GPP2 CDMA2000 (e.g., 1×RTT, 1×EV-DO, HRPD, eHRPD),Wi-Fi, WiMAX etc.

Base station 102 and other similar base stations (not shown) operatingaccording to one or more cellular communication technologies may thus beprovided as a network of cells, which may provide continuous or nearlycontinuous overlapping service to UE devices 106A-N and 107 and similardevices over a geographic area via one or more cellular communicationtechnologies.

Note that at least in some instances a UE device 106/107 may be capableof communicating using any of a plurality of wireless communicationtechnologies. For example, a UE device 106/107 might be configured tocommunicate using one or more of GSM, UMTS, CDMA2000, WiMAX, LTE, LTE-A,WLAN, Bluetooth, one or more global navigational satellite systems(GNSS, e.g., GPS or GLONASS), one and/or more mobile televisionbroadcasting standards (e.g., ATSC-M/H), etc. Other combinations ofwireless communication technologies (including more than two wirelesscommunication technologies) are also possible. Likewise, in someinstances a UE device 106/107 may be configured to communicate usingonly a single wireless communication technology.

The UEs 106A and 106B are typically handheld devices such as smartphones or tablets, but may be any of various types of device withcellular communications capability. The UE 106B may be configured tocommunicate with the UE device 107, which may be referred to as anaccessory device 107. The accessory device 107 may be any of varioustypes of wireless devices, typically a wearable device that has asmaller form factor, and may have limited battery, output power and/orcommunications abilities relative to UEs 106. As one common example, theUE 106B may be a smart phone carried by a user, and the accessory device107 may be a smart watch worn by that same user. The UE 106B and theaccessory device 107 may communicate using any of various short rangecommunication protocols, such as Bluetooth or Wi-Fi.

The accessory device 107 includes cellular communication capability andhence is able to directly communicate with cellular base station 102.However, since the accessory device 107 is possibly one or more ofcommunication, output power and/or battery limited, the accessory device107 may in some instances selectively utilize the UE 106B as a proxy forcommunication purposes with the base station 102 and hence to thenetwork 100. In other words, the accessory device 107 may selectivelyuse the cellular communication capabilities of the UE 106B to conductits cellular communications. The limitation on communication abilitiesof the accessory device 107 can be permanent, e.g., due to limitationsin output power or the radio access technologies (RATs) supported, ortemporary, e.g., due to conditions such as current battery status,inability to access a network, or poor reception.

FIG. 2 illustrates an example accessory device 107 in communication withbase station 102. The accessory device 107 may be a wearable device suchas a smart watch. The accessory device 107 may comprise cellularcommunication capability and be capable of directly communicating withthe base station 102 as shown. When the accessory device 107 isconfigured to directly communicate with the base station, the accessorydevice may be said to be in “autonomous mode.”

The accessory device 107 may also be capable of communicating withanother device (e.g., UE 106), referred to as a proxy device orintermediate device, using a short range communications protocol; forexample, the accessory device 107 may according to some embodiments be“paired” with the UE 106. Under some circumstances, the accessory device107 may use the cellular functionality of this proxy device forcommunicating cellular voice/data with the base station 102. In otherwords, the accessory device 107 may provide voice/data packets intendedfor the base station 102 over the short range link to the UE 106, andthe UE 106 may use its cellular functionality to transmit (or relay)this voice/data to the base station on behalf of the accessory device107. Similarly, the voice/data packets transmitted by the base stationand intended for the accessory device 107 may be received by thecellular functionality of the UE 106 and then may be relayed over theshort range link to the accessory device. As noted above, the UE 106 maybe a mobile phone, a tablet, or any other type of hand-held device, amedia player, a computer, a laptop or virtually any type of wirelessdevice. When the accessory device 107 is configured to indirectlycommunicate with the base station using the cellular functionality of anintermediate or proxy device, the accessory device may be said to be in“relay mode.”

The UE 106 and/or 107 may include a device or integrated circuit forfacilitating cellular communication, referred to as a cellular modem.The cellular modem may include one or more processors (processorelements) and various hardware components as described herein. The UE106 and/or 107 may perform any of the method embodiments describedherein by executing instructions on one or more programmable processors.Alternatively, or in addition, the one or more processors may be one ormore programmable hardware elements such as an FPGA (field-programmablegate array), or other circuitry, that is configured to perform any ofthe method embodiments described herein, or any portion of any of themethod embodiments described herein. The cellular modem described hereinmay be used in a UE device as defined herein, a wireless device asdefined herein, or a communication device as defined herein. Thecellular modem described herein may also be used in a base station orother similar network side device.

The UE 106 and/or 107 may include one or more antennas for communicatingusing two or more wireless communication protocols or radio accesstechnologies. In some embodiments, the UE device 106/107 might beconfigured to communicate using a single shared radio. The shared radiomay couple to a single antenna, or may couple to multiple antennas(e.g., for MIMO) for performing wireless communications. Alternatively,the UE device 106/107 may include two or more radios. Otherconfigurations are also possible.

The accessory device 107 may be any of various types of devices that, insome embodiments, has a smaller form factor relative to a conventionalsmart phone, and may have one or more of limited communicationcapabilities, limited output power, or limited battery life relative toa conventional smart phone. As noted above, in some embodiments, theaccessory device 107 is a smart watch or other type of wearable device.As another example, the accessory device 107 may be a tablet device,such as an iPad, with Wi-Fi capabilities (and possibly limited or nocellular communication capabilities), which is not currently near aWi-Fi hotspot and hence is not currently able to communicate over Wi-Fiwith the Internet. Thus, as defined above, the term “accessory device”refers to any of various types of devices that in some instances havelimited or reduced communication capabilities and hence may selectivelyand opportunistically utilize the UE 106 as a proxy for communicationpurposes for one or more applications and/or RATs. When the UE 106 iscapable of being used by the accessory device 107 as a proxy, the UE 106may be referred to as a companion device to the accessory device 107.

FIG. 3—Example Block Diagram of a UE Device

FIG. 3 illustrates one possible block diagram of an UE device, such asUE device 106 or 107. As shown, the UE device 106/107 may include asystem on chip (SOC) 300, which may include portions for variouspurposes. For example, as shown, the SOC 300 may include processor(s)302 which may execute program instructions for the UE device 106/107,and display circuitry 304 which may perform graphics processing andprovide display signals to the display 360. The SOC 300 may also includemotion sensing circuitry 370 which may detect motion of the UE 106, forexample using a gyroscope, accelerometer, and/or any of various othermotion sensing components. The processor(s) 302 may also be coupled tomemory management unit (MMU) 340, which may be configured to receiveaddresses from the processor(s) 302 and translate those addresses tolocations in memory (e.g., memory 306, read only memory (ROM) 350, flashmemory 310). The MMU 340 may be configured to perform memory protectionand page table translation or set up. In some embodiments, the MMU 340may be included as a portion of the processor(s) 302.

As shown, the SOC 300 may be coupled to various other circuits of the UE106/107. For example, the UE 106/107 may include various types of memory(e.g., including NAND flash 310), a connector interface 320 (e.g., forcoupling to a computer system, dock, charging station, etc.), thedisplay 360, and wireless communication circuitry 330 (e.g., for LTE,LTE-A, CDMA2000, Bluetooth, Wi-Fi, NFC, GPS, etc.).

The UE device 106/107 may include at least one antenna, and in someembodiments multiple antennas 335 a and 335 b, for performing wirelesscommunication with base stations and/or other devices. For example, theUE device 106/107 may use antennas 335 a and 335 b to perform thewireless communication. As noted above, the UE device 106/107 may insome embodiments be configured to communicate wirelessly using aplurality of wireless communication standards or radio accesstechnologies (RATs).

The wireless communication circuitry 330 may include Wi-Fi Logic 332, aCellular Modem 334, and Bluetooth Logic 336. The Wi-Fi Logic 332 is forenabling the UE device 106/107 to perform Wi-Fi communications on an802.11 network. The Bluetooth Logic 336 is for enabling the UE device106/107 to perform Bluetooth communications. The cellular modem 334 maybe a lower power cellular modem capable of performing cellularcommunication according to one or more cellular communicationtechnologies.

As described herein, UE 106/107 may include hardware and softwarecomponents for implementing embodiments of this disclosure. For example,one or more components of the wireless communication circuitry 330(e.g., Wi-Fi logic 332, cellular modem 334, BT logic 336) of the UEdevice 106/107 may be configured to implement part or all of the methodsdescribed herein, e.g., by a processor executing program instructionsstored on a memory medium (e.g., a non-transitory computer-readablememory medium), a processor configured as an FPGA (Field ProgrammableGate Array), and/or using dedicated hardware components, which mayinclude an ASIC (Application Specific Integrated Circuit).

FIG. 4—Block Diagram of a Base Station

FIG. 4 illustrates an example block diagram of a base station 102,according to some embodiments. It is noted that the base station of FIG.4 is merely one example of a possible base station. As shown, the basestation 102 may include processor(s) 404 which may execute programinstructions for the base station 102. The processor(s) 404 may also becoupled to memory management unit (MMU) 440, which may be configured toreceive addresses from the processor(s) 404 and translate thoseaddresses to locations in memory (e.g., memory 460 and read only memory(ROM) 450) or to other circuits or devices.

The base station 102 may include at least one network port 470. Thenetwork port 470 may be configured to couple to a telephone network andprovide a plurality of devices, such as UE devices 106/107, access tothe telephone network as described above in FIGS. 1 and 2.

The network port 470 (or an additional network port) may also oralternatively be configured to couple to a cellular network, e.g., acore network of a cellular service provider. The core network mayprovide mobility related services and/or other services to a pluralityof devices, such as UE devices 106/107. In some cases, the network port470 may couple to a telephone network via the core network, and/or thecore network may provide a telephone network (e.g., among other UEdevices serviced by the cellular service provider).

The base station 102 may include at least one antenna 434, and possiblymultiple antennas. The antenna(s) 434 may be configured to operate as awireless transceiver and may be further configured to communicate withUE devices 106/107 via radio 430. The antenna(s) 434 communicates withthe radio 430 via communication chain 432. Communication chain 432 maybe a receive chain, a transmit chain or both. The radio 430 may beconfigured to communicate via various wireless communication standards,including, but not limited to, LTE, LTE-A, GSM, UMTS, CDMA2000, Wi-Fi,etc.

The base station 102 may be configured to communicate wirelessly usingmultiple wireless communication standards. In some instances, the basestation 102 may include multiple radios, which may enable the basestation 102 to communicate according to multiple wireless communicationtechnologies. For example, as one possibility, the base station 102 mayinclude an LTE radio for performing communication according to LTE aswell as a Wi-Fi radio for performing communication according to Wi-Fi.In such a case, the base station 102 may be capable of operating as bothan LTE base station and a Wi-Fi access point. As another possibility,the base station 102 may include a multi-mode radio which is capable ofperforming communications according to any of multiple wirelesscommunication technologies (e.g., LTE and Wi-Fi, LTE and UMTS, LTE andCDMA2000, UMTS and GSM, etc.).

As described further subsequently herein, the BS 102 may includehardware and software components for implementing or supportingimplementation of features described herein. The processor 404 of thebase station 102 may be configured to implement or supportimplementation of part or all of the methods described herein, e.g., byexecuting program instructions stored on a memory medium (e.g., anon-transitory computer-readable memory medium). Alternatively, theprocessor 404 may be configured as a programmable hardware element, suchas an FPGA (Field Programmable Gate Array), or as an ASIC (ApplicationSpecific Integrated Circuit), or a combination thereof. Alternatively(or in addition) the processor 404 of the BS 102, in conjunction withone or more of the other components 430, 432, 434, 440, 450, 460, 470may be configured to implement or support implementation of part or allof the features described herein.

FIG. 5—Flowchart

FIG. 5 is a flowchart diagram illustrating a method for an accessorydevice to recover from out of service conditions, according to someembodiments. In various embodiments, some of the elements of the methodsshown may be performed concurrently, in a different order than shown,may be substituted for by other method elements, or may be omitted.Additional method elements may also be performed as desired.

Aspects of the method of FIG. 5 may be implemented by a wireless device,such as a UE 106 or 107 illustrated in and described with respect toFIGS. 1-3, or more generally in conjunction with any of the computersystems or devices shown in the above Figures, among other devices, asdesired. As shown, the method may operate as follows.

In 502, an accessory device may pair with another (“second” or “paired”)device using one or more short range wireless communicationtechnologies. Pairing the accessory device with the second device maycreate a link between the devices such that the devices may be able towirelessly communicate when within communication range of one another.According to some embodiments, a paired relationship between devices mayoptionally additionally include or enable one or more furthercharacteristics, such as any or all of one or more shared settings, userprofiles and/or accounts, data synchronization between the devices, etc.

The accessory device and the second device may be capable ofcommunicating with each other using any or all of Bluetooth, Wi-Fi, nearfield communication (NFC), and/or any of various other possible shortrange communication protocols, according to some embodiments.Additionally, each of the accessory device and the second device may becapable of performing cellular communication, according to someembodiments.

Although each of the accessory device and the second device may becapable of communicating according to multiple wireless communicationtechnologies, at least according to some embodiments, the accessorydevice may have different characteristics than the second device thatmay affect their respective preferred usage patterns and relationships.For example, as one possibility, the accessory device might be a smartwatch or other wearable device, while the second device might be a smartphone, and the accessory device might have more limited battery capacityand degraded antenna performance relative to the second device.

In accordance with such potentially differing characteristics, it may(at least some of the time) be desirable for the accessory device toutilize the cellular service communication capabilities of the seconddevice when available instead of performing cellular communicationdirectly, and/or to obtain assistance from the second device tofacilitate acquisition of cellular service by the accessory device.Furthermore, it may be desirable to prepare in advance for possiblescenarios when the accessory device may temporarily lose cellularservice and/or the pairing connection with the second device, such as ifa user of the accessory device brings the accessory device along withthem (e.g., on a run, hike, etc.) while leaving the second device behind(e.g., at home).

Accordingly, in 504, the accessory device may receive (e.g., using ashort range wireless communication technology) cellular communicationsystem selection information from the second device, and may store thereceived information. The cellular communication system selectioninformation may include any or all of various possible types ofinformation available at the second device that may be of assistance tothe accessory device in discovering, acquiring, and/or attaching to acell from which cellular service may be obtained. For example, thecellular communication system selection information may includeindications of any or all of a cell identifier, frequency, and/or RAT ofa cell on which the second device is currently (or was most recently)camped, a list of neighboring cells to the serving cell of the seconddevice (e.g., potentially including inter-frequency and/orintra-frequency neighboring cells operating according to the same or adifferent RAT (e.g., LTE, WCDMA, etc.) as the serving cell), a list offrequencies on which the second device has detected cellular systeminformation (possibly including one or more characteristics, such assignal strength, of those systems detected), a list of candidatecellular system frequencies associated with a location of the seconddevice, a public land mobile network (PLMN) on which the second deviceis currently (or was most recently) registered (e.g., a RPLMN of thesecond device), and/or any of various other kinds of information, asdesired.

According to some embodiments, the second device may occasionallyprovide updated cellular communication system selection information tothe accessory device while they are paired, e.g., in order to ensurethat the accessory device has the most recent cellular communicationsystem selection information available from the second device. Note thatif desired, such data transfers may be performed opportunisticallyand/or as background activities (e.g., after the accessory device andthe second device are already active and/or communicating, such as inresponse to user activity), which may help conserve battery power at oneor both of the accessory device and the second device. Such updates maybe performed at any of various possible (e.g., approximate or precise)periodicities, such as once per week, once per day, once per hour, onceper five minutes, etc. As another (alternative or additional)possibility, updated cellular communication system selection informationmay be provided to the accessory device in response to a triggeringevent, such as an initial pairing between the accessory device and thesecond device, a user request, an upcoming scheduled event (e.g., a‘run’, ‘hike’, or other activity determined to increase a likelihood ofthe accessory device and the second device temporarily losing theirpairing) stored in one or both of the accessory device or the seconddevice, etc.

In 506, the accessory device may determine that it has lost cellularcommunication service. For example, the signal strength of a cell towhich the accessory device had been attached may have decreased (e.g.,due to movement of the accessory device away from the cell, increasedinterference, etc.) such that the accessory device is no longer able tocommunicate with the base station providing the cell, and the accessorydevice may not be aware of any suitable neighboring cells. According tosome embodiments, the accessory device may also have lost its pairingwith the second device. For example, as previously discussed, theaccessory device may be transported (e.g., on a jog, hike, bike ride,etc.) beyond communication range of the second device.

In 508, the accessory device may attempt to regain cellularcommunication service. As part of its attempt to regain cellularcommunication service, the accessory device may utilize the cellularcommunication system selection information received from the seconddevice, e.g., in addition to cellular communication system selectionhistory and location data from the accessory device. For example, theaccessory device may perform a cellular communication service scan ofone or more frequencies on which one or more cells may be deployed basedat least in part on the cellular communication system selectioninformation received from the second device, e.g., including some or allfrequencies from an acquisition list (cells for which system informationhas previously been detected) and/or a neighbor list (cells indicated tobe neighbor cells to the serving cell) for each of the accessory deviceand/or the second device. Such a cellular communication service scan mayinclude scanning one or more frequencies (e.g., identified by absoluteradio frequency channel number (ARFCN) or enhanced ARFCN (EARFCN)) todetermine if a cellular system is present at each scanned frequency, and(at least in some instances) attempting to acquire system informationand potentially attaching to a cell if such acquisition of systeminformation for the cell is successful.

As previously noted, at least according to some embodiments, thecellular communication system selection information may include anindication of possible candidate frequencies associated with a locationof the second device. Additionally or alternatively, the accessorydevice may have location-based information indicating possible candidatefrequencies associated with one or more locations or regions storedlocally (e.g., as a database on an application processor of theaccessory device, as one possibility). For example, location-assistedfrequency lists including information identifying frequencies on whichcells may be deployed may be available on the accessory device for eachof one or more “tiles” (e.g., rectangular regions that may be 50 km×50km, 20 km×20 km, 10 km×10 km, or any other desired dimension).

Thus, the accessory device may be able to determine its location (e.g.,using a global navigational satellite system (GNSS), based oninformation from a recently used cellular base station or Wi-Fi accesspoint, by tracking motion of the accessory device from a reference pointusing a motion processor, and/or according to any of a variety of othertechniques), and may select one or more such location-assisted frequencylists associated with the current location of the accessory device aspart of the cellular communication service scan. For example, a listassociated with a tile in which the current location of the accessorydevice is located may be selected, and potentially lists for one or moretiles adjacent to the tile in which the current location of theaccessory device is located may also be selected, such as any tileswithin a 50 km (or 20 km, or 10 km, etc.) radius of the current locationof the accessory device.

According to some embodiments, either or both of cellular communicationsystem selection information obtained from the second device orseparately obtained location based cellular communication systemselection information may be filtered prior to use in the cellularcommunication service scan, e.g., in order to enhance the efficiency ofthe cellular communication service scan.

For example, some or all of the candidate frequencies (e.g., includingthose determined from the cellular communication system selectioninformation received from the second device and/or determined based onthe location of the accessory device) may be filtered based on apreferred radio access technology (e.g., non-LTE or LTE-A frequenciesmay be removed, as one possibility) and/or a preferred PLMN or set ofPLMNs (e.g., non home PLMN (HPLMN) or equivalent home PLMN (EHPLMN)frequencies may be removed, as one possibility), if desired.

As another possibility, some or all of the possible candidatefrequencies may be filtered based on physical characteristics of theaccessory device that differ from the second device. For example, aspreviously discussed, in some instances an accessory device may have asmaller and/or lower powered antenna arrangement than a device withwhich it is paired. In such cases, it may make sense to apply a signalstrength threshold based filter to the list of frequencies on which thesecond device has previously detected cellular system information, e.g.,to remove frequencies with signal strength below a signal strengththreshold specific to the accessory device. For example, as onenon-limiting possibility, the second device might be able to acquire afrequency with at least 103 dB RSSI, but the accessory device mightrequire a 113 dB RSSI, and so may remove, mark as non-acceptable, and/orignore frequencies with RSSI below 113 dB from the list of frequencieson which the second device has previously detected cellular systeminformation rather than scanning those frequencies as part of thecellular communication service scan, at least initially. As anotherexample, the accessory device may be technologically limited, such thatit can only perform cellular communication according to certain radioaccess technologies (e.g., the accessory device may not support one ormore older (legacy) RATs, and/or may itself be a legacy device that doesnot support one or more newer RATs). In such a case, candidatefrequencies associated with technologies not supported by the accessorydevice may be filtered out based on the physical characteristics of theaccessory device.

As a further consideration, if location based data is used for thecellular communication service scan, it may be useful to consider themotion state of the accessory device, as it may affect the validity ofthe location based data. For example, if a location based set ofcandidate frequencies is determined based on a current location of theaccessory device at one point in time, but the accessory device ismoving rapidly, that location based set of candidate frequencies mayquickly become stale and result in inefficient scanning. If theaccessory device is stationary or only slowly moving, such informationmay have a longer useful life before becoming stale. Thus, according tosome embodiments, the accessory device may determine a motion state ofthe accessory device, e.g., using motion sensing circuitry, such as oneor more accelerometers, gyroscopes, vibration sensors, and/or othermotion sensing components, which may be capable of sensing motionmagnitude and/or type for various types of motion. Based on the motionstate, the accessory device may determine an expiration time for (orinitiate a timer, or otherwise track when to discard) its location basedscan list based on the motion state of the accessory device. Forexample, a location based scan list may be considered valid for 5minutes in a high motion state, or 15 minutes in a moderate motionstate, or an hour in a stationary or nearly stationary motion state, asone possibility. Note that these values are illustrative only, and anynumber of other values and motion states may be used according tovarious embodiments.

According to some embodiments, once a location based scan list becomesstale, if the accessory device is still out of service, a new locationbased scan list may be prepared. For example, a current location of theaccessory device may be determined anew, and any desired candidatefrequency list(s) associated with that location may be filtered usingany desired filtering criteria to generate the new location based scanlist.

In some embodiments, the cellular communication service scan may includemultiple phases. For example, in a first phase, only a (potentiallyfiltered) set of those frequencies on which the accessory device and/orsecond device has previously detected cellular communication systeminformation, those frequencies on which neighbor cells for the accessorydevice and/or the second device are indicated to be deployed, and thosefrequencies associated with the location of the accessory device may bescanned. The first phase may last until a timer associated with thefirst phase expires or until cellular service is obtained. If cellularservice has still not been obtained when the first phase ends, a secondphase may begin in which the scan may be broadened to (e.g., also)include one or more band scans. Note that the band(s) scanned may alsobe filtered based on physical and/or subscription characteristics of theaccessory device, if desired.

According to some embodiments, the set(s) of frequencies scanned duringthe first phase and/or the second phase may be ordered based on one ormore considerations, e.g., to prioritize frequencies scanned forimproved efficiency. For example, depending on the scan duration (e.g.,length of time for which the accessory device has been out-of-service)and the motion of the accessory device while out-of-service, thosefrequencies selected from acquisition list database(s), neighbor listdatabases(s), and/or location based list database(s) of the accessorydevice and/or second device may be ordered depending on the relativelikelihood of acquiring service from a frequency from each of thoserespective sources. As one possibility, during the first phase, the setmay initially be ordered such that frequencies from the acquisition listdatabase(s) are first in the order, followed by frequencies from theneighbor list database(s), further followed by frequencies from thelocation based list database(s). During the second phase, the set may beinitially be ordered similarly, with PLMN list database(s)frequencies/bands may be appended at the end of the order. Alternatively(or in addition), the set may have a different order and/or bere-ordered depending on the circumstances of the accessory device. Forexample, if sufficient motion has been detected, frequencies from thelocation based list database(s) may be moved below frequencies/bandsfrom the PLMN list database(s) in the scan order, e.g., since thelocation information based on which those frequencies were selected mayno longer be relevant (or may be less relevant) due to the motion of theaccessory device. Other orders and ordering algorithms are alsopossible.

In some embodiments, the scan may be performed over time in multiple“scan steps,” which may occur periodically (e.g., every 10 s, every 20s, every 60 s, etc.) while the accessory device is out-of-service. Ineach scan step, a certain (e.g., predetermined, or possibly dynamicallyselected) number (e.g., 5, 10, 15, etc.) of frequencies may be scanned,e.g., starting from the top of the (e.g., ordered) set of frequencies tobe scanned, such that during each scan step a portion of the frequenciesof the total set of frequencies may be scanned. Once all of thefrequencies in the set have been scanned (and assuming service has notyet been acquired), those frequencies from the top of the set may againbe scanned, and so on. If (e.g., based on device motion and/or durationof OOS) the scan set is updated and/or reordered at some point duringthe scan, the new set and/or order may apply beginning with the nextrepetition through the scan list, according to some embodiments.

Note that while a multi-phase cellular service scan may be similar instructure to a cellular service scan that might be implemented by ahigher performance device (such as the second device, according to someembodiments), the relative phase lengths for the accessory device andthe second device may differ. For example, the first phase (e.g., thelength of time before the scan is broadened to include band scanning)may be longer for the accessory device than for the second device, e.g.,since targetted scanning of those frequencies that are most likely toresult in the accessory device finding cellular service, such as mayoccur in the first phase, may be more power efficient than broader bandscans, such as may occur in the second phase, and power efficiency maybe more important for the accessory device than for the second device,at least according to some embodiments.

As a still further possible consideration, the accessory device mayselect (or modify) its cellular communication service scan techniquedepending at least in part on whether the second device had cellularservice when the cellular communication system selection information wasreceived from the second device, and/or depending at least in part onwhat RAT the second device was using when the cellular communicationsystem selection information was received from the second device. Forexample, if the second device had service and was camped on a preferredRAT (e.g., LTE, LTE-A, or any other preferred RAT), the accessory devicemay initially scan just those (potentially filtered) frequencies onwhich the second device has previously detected cellular communicationsystem information, since in such a case it may be relatively likelythat there is a good candidate cell for the accessory device among thosefrequencies. However, if the second device is camped on a non-preferredRAT, or does not have service, the accessory device may initially scanboth those (potentially filtered) frequencies on which the second devicehas previously detected cellular communication system information and a(potentially filtered) set of frequencies associated with the locationof the accessory device, since in such a case it may be less likely thatthere is a good candidate cell for the accessory device among just thosefrequencies on which the second device has previously detected cellularcommunication system information (e.g., since the second device may nothave been able to obtain service according to the preferred RAT evenwith its potentially greater resources).

In addition to the above-described exemplary embodiments, furtherembodiments of the present disclosure may be realized in any of variousforms. For example some embodiments may be realized as acomputer-implemented method, a computer-readable memory medium, or acomputer system. Other embodiments may be realized using one or morecustom-designed hardware devices such as ASICs. Still other embodimentsmay be realized using one or more programmable hardware elements such asFPGAs.

In some embodiments, a non-transitory computer-readable memory mediummay be configured so that it stores program instructions and/or data,where the program instructions, if executed by a computer system, causethe computer system to perform a method, e.g., any of a methodembodiments described herein, or, any combination of the methodembodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets.

In some embodiments, a device (e.g., a UE 106 or 107) may be configuredto include a processor (or a set of processors) and a memory medium,where the memory medium stores program instructions, where the processoris configured to read and execute the program instructions from thememory medium, where the program instructions are executable toimplement any of the various method embodiments described herein (or,any combination of the method embodiments described herein, or, anysubset of any of the method embodiments described herein, or, anycombination of such subsets). The device may be realized in any ofvarious forms.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

What is claimed is:
 1. An apparatus, comprising a processing element configured to cause an accessory device to: receive cellular communication system selection information from a paired device, wherein the cellular communication system selection information comprises at least information identifying a current cell and a radio access technology (RAT) on which the paired device is camped; store the cellular communication system selection information received from the paired device; determine that the accessory device has lost a pairing with the paired device; determine that the accessory device has lost cellular communication service; and perform a cellular communication service scan utilizing the cellular communication system selection information received from the paired device, wherein the cellular communication service scan is performed while the accessory device has lost the pairing with the paired device and has lost cellular communication service.
 2. The apparatus of claim 1, wherein the information identifying the current cell comprises information indicating at least one of a cell identifier of the current cell or a frequency of the current cell.
 3. The apparatus of claim 1, wherein the system selection information received from the paired device further comprises at least one of: a registered public land mobile network entry (RPLMN) for the paired device; a stored frequency list comprising information identifying a plurality of frequencies on which the paired device has previously detected cellular communication system information; a neighbor frequency list comprising information identifying a plurality of frequencies on which neighboring cells to a serving cell of the paired device are deployed; or a location assisted frequency list comprising information identifying a plurality of frequencies associated with a location of the paired device.
 4. The apparatus of claim 1, wherein the processing element is further configured to cause the accessory device to: filter the cellular communication system selection information from the paired device based on one or more characteristics of accessory device that differ from the paired device.
 5. The apparatus of claim 4, wherein the one or more characteristics comprise a degraded antenna performance of the accessory device relative to the paired device, wherein filtering the cellular communication system selection information comprises removing system selection candidate frequencies with signal strength below a signal strength threshold specific to the accessory device.
 6. The apparatus of claim 1, wherein the processing element is further configured to cause the accessory device to: determine a current location of the accessory device; filter a list of frequencies associated with the current location of the accessory device based on a preferred RAT and a preferred public land mobile network (PLMN) of the accessory device; and perform the cellular communication service scan based at least in part on the filtered list of frequencies associated with the current location of the accessory device.
 7. The apparatus of claim 6, wherein the processing element is further configured to cause the accessory device to: determine a motion state of the accessory device; and determine an expiration time of the filtered list of frequencies associated with the current location of the accessory device based on the motion state of the accessory device.
 8. The apparatus of claim 7, wherein the processing element is further configured to cause the accessory device to: determine that the filtered list of frequencies associated with the current location of the accessory device has expired and that the accessory device has still lost cellular communication service; determine a new current location of the accessory device; filter a list of frequencies associated with the new current location of the accessory device based on the preferred radio access technology (RAT) and the preferred public land mobile network (PLMN); and perform further cellular communication service scanning based at least in part on the filtered list of frequencies associated with the new current location of the accessory device.
 9. The apparatus of claim 1, wherein to perform a cellular communication service scan utilizing the system selection information received from the paired device the accessory device is further configured to: select a cellular communication service scan algorithm from at least two possible cellular communication service scan algorithms based on the RAT on which the paired device was camped.
 10. The apparatus of claim 1, wherein the processing element is further configured to cause the accessory device to: determine that a predetermined period of time has passed and the accessory device has not regained cellular communication service; broaden the cellular communication service scan to include one or more band scans based on determining that the predetermined period of time has passed, wherein the predetermined period of time is greater than a period of time of unsuccessful cellular communication service scanning after which the paired device broadens a cellular communication service scan to include one or more band scans.
 11. An accessory device, comprising: an antenna; a radio coupled to the antenna; and a processing element coupled to the radio; wherein the accessory device is configured to: receive cellular communication system selection information from a paired device; store the cellular communication system selection information received from the paired device; determine that the accessory device has lost cellular communication service; determine that the accessory device has lost a pairing with the paired device; and perform a cellular communication service scan utilizing the cellular communication system selection information received from the paired device, wherein the cellular communication service scan is performed while the accessory device has lost the pairing with the paired device and has lost cellular communication service.
 12. The accessory device of claim 11, wherein the cellular communication system selection information comprises information identifying: a current cell on which the paired device is camped; a radio access technology (RAT) of the current cell on which the paired device is camped; a registered public land mobile network entry (RPLMN) for the paired device; a plurality of frequencies on which the paired device has previously detected cellular communication system information; a plurality of frequencies on which neighboring cells to the current cell on which the paired device is camped are deployed; and a plurality of frequencies associated with a location of the paired device.
 13. The accessory device of claim 11, wherein the accessory device is further configured to: filter the cellular communication system selection information from the paired device based on one or more characteristics of accessory device that differ from the paired device.
 14. The accessory device of claim 11, wherein the accessory device is further configured to: determine motion information for the accessory device; and modify the cellular communication service scan based on the motion information for the accessory device.
 15. A memory medium comprising program instructions that, when executed, cause an accessory device to: pair with a second device using a short range wireless communication technology; receive cellular communication system selection information from the second device using the short range wireless communication technology; store the cellular communication system selection information received from the second device; determine that the accessory device does not have cellular communication service; determine a current location and current motion state of the accessory device; determine a plurality of frequencies associated with the current location of the accessory device, wherein the plurality of frequencies associated with the current location are determined based on one or more of the cellular communication system selection information received from the second device or location database information stored in a memory of the accessory device; determine a time at which the determined plurality of frequencies associated with the current location are considered to be stale based on the current motion state of the accessory device; and based on determining the time at which the determined plurality of frequencies associated with the current location are considered to be stale, perform a cellular communication service scan utilizing the cellular communication system selection information received from the second device.
 16. The memory medium of claim 15, wherein the cellular communication system selection information comprises at least information indicating a plurality of frequencies on which the second device has previously detected cellular communication system information, wherein when executed, the program instructions further cause the accessory device to: filter the plurality of frequencies on which the second device has previously detected cellular communication system information to remove frequencies detected with signal strength below a signal strength threshold associated with the accessory device; and perform the cellular communication service scan utilizing the filtered plurality of frequencies on which the second device has previously detected cellular communication system information.
 17. The memory medium of claim 16, wherein the cellular communication system selection information further comprises at least information indicating a radio access technology (RAT) on which the second device most recently camped, wherein when executed, the program instructions further cause the accessory device to: initially scan just the filtered plurality of frequencies on which the second device has previously detected cellular communication system information when the RAT on which the second device most recently camped is a preferred RAT; initially scan both the filtered plurality of frequencies on which the second device has previously detected cellular communication system information and a plurality of frequencies associated with a current location of the accessory device when the RAT on which the second device most recently camped is not a preferred RAT.
 18. The memory medium of claim 15, wherein when executed, the program instructions further cause the accessory device to: determine a set of frequencies to be scanned; and determine a scan order for the set of frequencies to be scanned, wherein the scan order is determined based at least in part on a duration for which the accessory device has not had cellular communication service and on motion of the accessory device since the accessory device has not had cellular communication service, wherein the cellular communication service scan utilizes the determined scan order.
 19. An apparatus for configuration in an accessory device, comprising: one or more processing elements, wherein the one or more processing elements are configured to: receive cellular communication system selection information from a paired device; store the cellular communication system selection information received from the paired device; filter the cellular communication system selection information from the paired device based on one or more characteristics of accessory device that differ from the paired device; determine that the accessory device has lost cellular communication service; and perform a cellular communication service scan utilizing the filtered cellular communication system selection information.
 20. The apparatus of claim 19, wherein the cellular communication system selection information comprises information identifying: a current cell on which the paired device is camped; a radio access technology (RAT) of the current cell on which the paired device is camped; a registered public land mobile network entry (RPLMN) for the paired device; a plurality of frequencies on which the paired device has previously detected cellular communication system information; a plurality of frequencies on which neighboring cells to the current cell on which the paired device is camped are deployed; and a plurality of frequencies associated with a location of the paired device.
 21. The apparatus device of claim 19, wherein the one or more processing elements are further configured to: determine motion information for the accessory device; and modify the cellular communication service scan based on the motion information for the accessory device.
 22. A memory medium comprising program instructions that, when executed, cause an accessory device to: pair with a second device using a short range wireless communication technology; receive cellular communication system selection information from the second device using the short range wireless communication technology; store the cellular communication system selection information received from the second device; determine that the accessory device does not have cellular communication service; determine a set of frequencies to be scanned; and determine a scan order for the set of frequencies to be scanned, wherein the scan order is determined based at least in part on a duration for which the accessory device has not had cellular communication service and on motion of the accessory device since the accessory device has not had cellular communication service; perform a cellular communication service scan utilizing the cellular communication system selection information received from the second device, wherein the cellular communication service scan utilizes the determined scan order.
 23. The memory medium of claim 22, wherein the cellular communication system selection information comprises at least information indicating a plurality of frequencies on which the second device has previously detected cellular communication system information, wherein when executed, the program instructions further cause the accessory device to: filter the plurality of frequencies on which the second device has previously detected cellular communication system information to remove frequencies detected with signal strength below a signal strength threshold associated with the accessory device; and perform the cellular communication service scan utilizing the filtered plurality of frequencies on which the second device has previously detected cellular communication system information.
 24. The memory medium of claim 23, wherein the cellular communication system selection information further comprises at least information indicating a radio access technology (RAT) on which the second device most recently camped, wherein when executed, the program instructions further cause the accessory device to: initially scan just the filtered plurality of frequencies on which the second device has previously detected cellular communication system information when the RAT on which the second device most recently camped is a preferred RAT; initially scan both the filtered plurality of frequencies on which the second device has previously detected cellular communication system information and a plurality of frequencies associated with a current location of the accessory device when the RAT on which the second device most recently camped is not a preferred RAT. 